This invention relates to a continuously operating press, preferably for the manufacture and/or printing, lamination or the like of a one or multiple layer board web of pre-manufactured material and/or raw material. Such presses are particularly used for the manufacture of particleboard, fiberboard, hardboard or the like, and indeed from a mat comprising particles containing lignocellulose and/or cellulose such as wood chips, wood fibers or the like and at least one dispersed binder.
Continuously operating presses are known in the art. For example U.S. Pat. No. 4,420,299 discloses a continuous operation press for manufacturing and/or coating, veneering, etc., a single-layer or a multiple-layer board web made of a mat which includes wood chips, wood fibers, etc. The press includes a carrying run of an upper belt which continuously circulates at a preset constant speed and a carrying run of a lower belt, with both belts preferably being made of steel. A friction reducing arrangement such as a slide or friction reducing coating extends over an entire width of a press area and is disposed on an upper and lower abutment, with the entering belts sliding over the friction reducing coating. A pressurized liquid lubricant is supplied to the friction reducing coating. The friction reducing coating extends over at least a main press area as well as a calibration area in which upper and lower slide coating extend parallel to one another. A friction reducing coating may also be provided in the pre-press area with the respective friction reducing coatings being bent or inclined so as to form a press gap. The lubricant is fed to the friction reducing surface of the friction reducing coating through openings formed in the friction reducing coating, with the openings not extending as far as the lateral edge of the friction reducing coating but being spaced therefrom.
U.S. Pat. No. 4,565,509 discloses a continuous operation press for the manufacture and treatment of a board web of prefabricated or raw material, wherein the board web is passed into an inlet region between the upper and lower stringers of upper and lower endless belts traveling at a predetermined velocity in the transport direction, wherein there is provided a smooth coating formed with grooves serving as a sliding surface located at least in the main press and calibration regions. The board web glides above the smooth coating with the aid of fluid lubricant, the lubricant being supplied to the smooth coating through supply openings and discharged therefrom through discharge openings. Each groove in the smooth coating is formed with an opening therein either as a supply or discharge opening, each groove having a lubricant supply opening being positioned adjacent a groove having a lubricant discharge opening. Means are provided for controlling the pressure in at least some of said grooves for generation of a counter-pressure.
In the press disclosed in U.S. Pat. No. 4,565,509 the pressure control means for a lubricant for generating a counter-pressure in the working gap of the press (which pressure control means are associated with each groove of the slide coating having a discharge opening or a supply opening), ensure that the surface forces acting on the press band and on the slide coating are more uniformly carried by the lubricant. This results in an extremely low coefficient of friction and a correspondingly uniform heating or cooling distribution of the lubricant which is an important factor in determining the quality of the pressed material. A further determining factor for the quality is moreover the maintenance of a constant thickness and speed of the lubricant pressure film. This requirement cannot be straightforwardly and sufficiently satisfied in practice for the most stringent demands, even when the pressure control means for the lubricant are ideally adjusted for the generation of a counter-pressure in the working gap of the press.
U.S. Pat. No. 4,850,848 discloses a continuously operating press in which endless bands are moved with constant speed around an upper and a lower press platen and a lubricant film is formed between the confronting press platen surfaces and the respectively associated endless band. The fluid which serves for the build up of the lubricant film is kept in this arrangement under a predeterminable hydrodynamic pressure in at least one press zone at the input side of the press, while a calibration zone is provided at the output side of the press in which the lubricant stands substantially only under static pressure.
U.S. Pat. No. 5,229,139 discloses a continuously operating press for pressing a mat by running the mat in a transport direction through the press, the mat having a width and a narrow edge surface parallel to the transport direction, the press comprising a lower endless press band having a mat supporting side and a lubricated side opposite the mat supporting side; an upper endless press band lying above the lower endless press band positioned so that the mat is pressed between the bands; a slide coating positioned adjacent the lubricated side and having a plurality of grooves positioned in an edge region of the slide coating and extending generally in the transport direction, the edge region being located lateral of the narrow edge surface of the mat when the mat is supported on the lower endless band; and a perpendicular groove oriented generally transverse to the transport direction and extending to a lateral edge of the slide coating to thereby expose the perpendicular groove to outside pressure for reducing the pressure of the lubricant in the edge region.
However, none of the continuously operating presses cited above teach or suggest that a phenyl-endblocked polydiorganosiloxane-polyphenylorganosiloxane random copolymer fluid can be used as the lubricant in the press.
Phenyl-containing siloxanes and their use as lubricants have been disclosed in the art. For example, in U.S. Pat. No. 4,898,956 discloses thermo-oxidatively stable polysiloxanes are prepared by adding certain zirconium compounds to the fluid. These zirconium compounds are of the organozirconium or siloxyzirconium types. Two methods for preparation of the fluids is discussed. The fluids of this invention are useful as heat transfer fluids, lubricants, or damping fluids. They have particular usefulness in applications that have a low surface area to volume ratio.
Sobolevskii et al. on pages 12-14 of the journal Plasticheskie Massy (1962) disclose the resistance to thermal oxidation of polymethylphenylsiloxanes having different endgroups.
U.S. Pat. No. 3,267,036 discloses a method of stabilizing a liquid polysiloxane of the group consisting of liquid methyl-methylphenylmethylchlorophenyl- and methylphenyl chlorophenyl polysiloxanes which comprises combining a liquid polysiloxane of the aforesaid group with a cerium methylhydrogen polysiloxane adduct prepared by a method comprising preparing a solution in benzene of the disproportionation products of cerous acetylacetonate monohydrate by heating from about 3 to 8 moles of said monohydrate in solution in an excess of benzene under reflux and bubbling of air there into until the resulting benzene solution is wine red in color, combining said resulting benzene solution of disproportionation products with a benzene solution of a methylhydrogen polysiloxane having from about 0.5 to 1.67% by weight of silane hydrogen and in proportions to yield a resultant benzene solution which contains about 3 to 8 atoms of cerium per mole of said methylhydrogen polysiloxane, and heating said resulting benzene solution under reflux for about one hour while bubbling air there into at a rate sufficient to maintain the cerium in the ceric state, which is in solution in a portion of the same liquid polysiloxane in proportions to form a fluid mixture which contains from about 0.01 to 0.05% by weight of cerium atoms, rapidly heating said fluid mixture to a temperature in the range of 270 to 280xc2x0 C. while bubbling air there into at a rate sufficient to maintain the cerium in the ceric state and oxidize silane hydrogen therein, and continuing the heating at said temperature and the bubbling of air there into until the resulting fluid is clear and free from silane hydrogen.
Commercial lubricants currently used in continuously operating presses typically contain a trimethylsiloxy-endblocked polydimethylsiloxane-polyphenylmethylsiloxane random copolymer fluid and a stabilizing additive such as an iron compound. These lubricants have superior longevity versus prior lubricants, but still degrade with time and conditions of use (such as high temperatures and exposure to oxygen and contaminants). This degradation takes the form of an increase in fluid viscosity and a loss of fluid volume (in practice, volume loss is a combination of fluid breakdown and subsequent evaporation of some of the breakdown products plus system losses due to filter changes, system leaks, etc.), requiring make-up fluid addition and eventually partial or full fluid change-out. However, there has been no disclosure of the use of a phenyl-endblocked polydiorganosiloxane-polyphenylorganosiloxane random copolymer fluid as a lubricant for use as in a continuously operating press.
In a first embodiment, this invention relates to a continuously operating press, preferably for the manufacture and/or printing, lamination or the like of a one or multiple layer board web of pre-manufactured material and/or raw material, the improvement comprising using as the lubricant a phenyl-endblocked polydiorganosiloxane-polyphenylorganosiloxane random copolymer fluid.
In a second embodiment, this invention relates to a continuously operating press, preferably for the manufacture and/or printing, lamination or the like of a one or multiple layer board web of pre-manufactured material and/or raw material, the improvement comprising using as the lubricant a composition comprising (i) a phenyl-endblocked polydiorganosiloxane-polyphenylorganosiloxane random copolymer fluid and (ii) at least one stabilizing agent.